This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has two, three or four possible answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Minnesota Commercial Driver’s Manual. Questions come from the chapters covering: Air Brakes and Combination Vehicles. The Air Brakes endorsement may be used with the Class A, B or C CDL.